Growth, Characterization, and Properties of Epitaxial Metal/Nitride Superlattices

本研究的目的是研究沉积外延单晶氮化物/金属超晶格中的层具有不同的滑移系的强化机制。 材料系统为NbN/Mo、NbN/W、VN/Cr、AlN/Mo和AlN/W，提供了Nb-B1/Nb-BCC和六方纤锌矿/Nb-BCC组合。使用（001）和（111）取向的MgO和W衬底。 将确定当用立方（001）层包围时AlN是否可以以立方结构生长。由于超晶格结构，这些材料应该表现出大的强度和硬度增强。层特性、强度和硬度之间的相关性将提供关于强化机制的新信息。 层晶格失配的变化（在包含合金VN-NbN或Cr-Mo层的超晶格中）用于产生具有相干和非相干界面的超晶格。 与先前研究的氮化物/氮化物超晶格不同，这些层是不混溶的，使得结构稳定并在高温下保持其期望的特性。结构和性能的研究与退火时间和温度进行了比较，结果与氮化物/氮化物超晶格的结果。在氮化物/氮化物超晶格中存在技术兴趣，其中早期结果显示在切削工具中相对于常规氮化物涂层的显著改进。

The aim of this research is to investigate strengthening mechanisms in deposited epitaxial single-crystal nitride/metal superlattices where the layers have different slip systems. Materials systems are NbN/Mo, NbN/W, VN/Cr, AlN/Mo, and AlN/W, providing both cubic-B1/cubic-BCC and hexagonal-wurtzite/cubic-BCC combinations. Both (001) and (111) oriented MgO and W substrates are used. It will be determined if AlN can be grown in a cubic structure when surrounded with cubic (001) layers. These materials should exhibit large strength and hardness enhancements due to the superlattice structure. Correlations between layer characteristics, strength, and hardness will provide new information on strengthening mechanisms. Changes in the layer lattice mismatch (in superlattices containing alloy VN-NbN or Cr-Mo layers) are used to produce superlattices with both coherent and incoherent interfaces. Unlike previously-studied nitride/nitride superlattices, these layers are immiscible such that the structures are stable and retain their desirable characteristics at high temperatures. Structure a nd property studies versus annealing time and temperature are carried out, and the results compared with results from nitride/nitride superlattices. %%% There is technological interest in nitride/nitride superlattices where early results show dramatic improvements over conventional nitride coatings in cutting tools.